refactored mocked plugin class out of IT class

Author: piergm

server/src/internalClusterTest/java/org/elasticsearch/search/fetch/subphase/highlight/HighlighterSearchIT.java

@@ -3777,12 +3777,4 @@ public FakeConstantFieldMapper.Builder getMergeBuilder() {
             return new FakeConstantFieldMapper.Builder(mappedFieldType.name());
         }
     }
-
-    public static class MockConstantKeywordMapperPlugin extends Plugin implements MapperPlugin {
-        @Override
-        public Map<String, Mapper.TypeParser> getMappers() {
-            return singletonMap(FakeConstantFieldType.CONTENT_TYPE, FakeConstantFieldMapper.PARSER);
-        }
-
-    }
 }

server/src/internalClusterTest/java/org/elasticsearch/search/fetch/subphase/highlight/MockConstantKeywordMapperPlugin.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.search.fetch.subphase.highlight;
+
+import org.elasticsearch.index.mapper.Mapper;
+import org.elasticsearch.plugins.MapperPlugin;
+import org.elasticsearch.plugins.Plugin;
+
+import java.util.Map;
+
+import static java.util.Collections.singletonMap;
+
+public class MockConstantKeywordMapperPlugin extends Plugin implements MapperPlugin {
+    @Override
+    public Map<String, Mapper.TypeParser> getMappers() {
+        return singletonMap(HighlighterSearchIT.FakeConstantFieldType.CONTENT_TYPE, HighlighterSearchIT.FakeConstantFieldMapper.PARSER);
+    }
+
+}